1. Field of the Invention
The present invention relates to an exposure method and apparatus which are used to manufacture semiconductor devices, liquid crystal display devices, or the like by photolithography and can be suitably applied to the scanning or stepping exposure method.
2. Related Background Art
In a conventional exposure method using photolithography to manufacture semiconductor devices, liquid crystal display devices, or the like, a photomask having an original pattern formed thereon and a photosensitive substrate coated with a photosensitive agent are positioned in accordance with the following procedures.
The relative positional relationship between positioning mask marks formed on the photomask and positioning substrate marks formed on the photosensitive substrate is measured in accordance with a plurality of combinations of the mask marks and the substrate marks. Subsequently, on the basis of the measurement result of the mask marks and the substrate marks, a correction value for appropriately correcting the positional relationship between the photomask and the photosensitive substrate, or the positional relationship between a pattern area where the original pattern on the photomask is located and a shot area where the image of the original pattern is projected on the photosensitive substrate is calculated using a method of least squares.
On the basis of the calculated correction value, the photomask and the photosensitive substrate are relatively moved. Alternatively, the imaging characteristics of an imaging optical system for projecting the image of the original pattern of the photomask on the photosensitive substrate are adjusted, thereby correcting the positional relationship between the photomask and the photosensitive substrate or the positional relationship between the pattern area of the photomask and the shot area of the photosensitive substrate. Subsequently, the image of the original pattern of the photomask is actually exposed on the photosensitive substrate.
A prior art associated with such an exposure method is described in detail in, e.g., "U.S. Pat. No. 4,566,795 (Japanese Patent Laid-Open No. 57-138134)".